docs(dogfood): sync reset_report schema + README for --orphans-only (PR #149 review)

Round 1 review found 2 doc gaps:
- docs/wire-schema/v1/reset_report.schema.json: 'orphans_only' missing
  from scope enum; orphans_purged/purged_paths properties absent
- README: --orphans-only not listed in the reset prose

Schema additions are additive minor (default values keep back-compat).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/wire-schema/v1/reset_report.schema.json

@@ -14,12 +14,18 @@
     "schema_version":           { "const": "reset_report.v1" },
     "scope":                    {
       "type": "string",
-      "enum": ["all", "data_only", "vector_only", "config_only"]
+      "enum": ["all", "data_only", "vector_only", "config_only", "orphans_only"]
     },
     "removed_paths":            {
       "type": "array",
       "items": { "type": "string" }
     },
-    "embedding_rows_truncated": { "type": "integer", "minimum": 0 }
+    "embedding_rows_truncated": { "type": "integer", "minimum": 0 },
+    "orphans_purged":           { "type": "integer", "minimum": 0, "default": 0 },
+    "purged_paths":             {
+      "type": "array",
+      "items": { "type": "string" },
+      "default": []
+    }
   }
 }